Accurate and rapid diagnostic tests help improve patient outcome and help contain the spread of disease. Recent adaptation of molecular methodologies has led to more accurate and sensitive molecular diagnostic tests. PCR, RT-PCR, DNA array and DNA sequencing have proven to be highly sensitive and specific. More recently, loop mediated isothermal amplification (LAMP) has proven to be an attractive technology for rapid detection of pathogens. Due to high sensitivity and rapid turnaround time, molecular diagnostic tests are increasingly being used in large clinical laboratories.
Molecular analysis of clinical samples for the detection of genetic materials typically involves nucleic acid amplification, which typically entails a series of steps starting at sample collection. Raw samples are rarely suitable for direct detection of nucleic acids, necessitating processing of the sample prior to nucleic acid amplification. Significant resources and time are spent for clinical sample processing that involves multiple mechanical, physical, and chemical treatments before a target nucleic acid can be amplified for detection. One common approach in sample processing has been suspending a small aliquot of the sample in sample buffer followed by filtration to remove particulate material. Such a method is utilized in the Illumigene Clostridium difficile Test manufactured by Meridian Biosciences (J. Clin. Microbiol. April 2012; 50(4): 1331-1335). However, such methods involve multiple steps, require operators to transfer a measured quantity from one step to the next, and are time consuming, making them unsuitable to be used at the point of care, such as emergency room, nursing homes, and physician's office. Another common approach to isolate nucleic acids from clinical samples has been cell lysis followed by binding to resins followed by washing and finally elution with buffer for subsequent application. Such a process is either carried out by a highly trained technician or requires expensive equipment for automation. Neither option is suitable in a point-of-care setting.
There has been a growing trend and desire to move clinical diagnostic tests out of large central laboratories to point-of-care settings for faster and optimal treatment decisions. Having a diagnostic test that can be run at the point of care is expected to lead to better outcomes for the patient and cost savings. For the sample processing system to be useful at the point-of-care setting, it must involve very few steps and preferably comprises a single device that combines multiple steps. Such a device also should be able to accommodate a wide variety of clinical samples such as blood, saliva, stool etc. A point-of-care device should not require measuring equipment for volume etc., as access to such equipment may not exist or operators may not have training to use such equipment.
The challenge in developing a point-of-care diagnostic test has been developing a test that is easy to conduct, is small enough to fit in a point-of-care setting, is low cost to adopt and run, can accommodate diverse clinical samples, and yet can retain the high sensitivity and rapid turnaround time of larger instruments used in central laboratories. The lack of a point-of-care molecular diagnostic test underlines the need for the methods and devices described herein.